Games and DLC that you obtained by entering a Steam CD key or downloading from Steam store are linked to your Steam account.
Even if you re-install Steam Client due to replacing your computer or re-installing Windows, you can download registered games and DLC from [Library] again by signing in to Steam with the same Steam account.
* There is no need to re-enter your Steam CD key.
If you forgot your Steam account name or password, use Steam® Support by clicking here.